for the z min:
check the autofocus sensors and make sure they are not pointing down too far to see each other. the mounting holes for the sensor can be too close to the edge on the radius and this causes the sensor to be out of alignment:
the brown and blue wires on the sensor array should be +24vdc(brn) and 0vdc(blu). the black wire on the receiver (right) side goes to the ruida dsp cn3 pin 4